Simplify the following expression: $7\sqrt{20}$.
First, try to factor a perfect square out of the radical. $= 7\sqrt{20}$ $= 7\sqrt{4 \cdot 5}$ Separate the radical and simplify. $= 7\sqrt{4} \cdot \sqrt{5}$ $= 7 \cdot 2 \cdot \sqrt{5}$ $= 14\sqrt{5}$